Laboratory-scale flash still for petroleum oil fractions



Aug. 27, 1-968 J. J. DU BOIS ETAL LABORATORY-SCALE FLASH STILL FORPETROLEUM OIL FRACTIONS 2 Sheets-Sheet 1 Filed Jan. 17, 1966 Jab A,GIN/8K Rabeel 7: Radian M11340, 777041 00, gaszea ATTORNEY J. DU B L 2Sheets-S e R m m R W w H fin A kc n a ATTORNEY b mm, 27

Aug 27, 1968 LABORATORY-SCALE FLASH STILL FOR PETROLEUM OIL FRACTIONSFiled Jan. 17, 1966 E v 3:55 A I u "I" r n llllll 4 United States Patent3,399,116 LABORATGRY-SCALE FLASH STILL FOR PETROLEUM OIL FRACTIONS JuleJ. Du Bois, Schenectady, N.Y., and John A. Glover,

Munster, and Robert J. Buchler, Whiting, Ind., assignors to SinclairResearch, Inc., New York, N.Y., a corporation of Delaware Filed Jan. 17,1966, Ser. No. 521,165 Claims. (Cl. 196-98) ABSTRACT OF THE DISCLOSURE Alaboratory scale flash still, employing a preheating coil surrounding aflash chamber with dual removing means, the preheating coil and flashchamber being substantially immersed in a molten salt heating medium,and means for maintaining the dual removing means at equalsubatmospheric pressures.

This invention relates to a laboratory scale flash distillation still.of improved utility in flashing such materials as reduced crudes, heavyresidues, and penetration asphalts. More particularly, this inventionconcerns a laboratory scale flash distillation still which can be usedto produce petroleum products of the quality generally expected fromcommercial operations.

For a long time there has been a need for a continuous laboratory scaleequilibrium flash distillation still which can be used for processingvarious heavy hydrocarbon crudes in performing general assay work. Sucha still is particularly necessary because bench scale reactor studies donot produce products in large enough volume to be utilized in the pilotplant scale flash distillation still. Some of the problems which haveacted as a deterrent to the construction of such a still have been theoverall poor operability of previously constructed small stills and ageneral reluctance to operate in a distillation laboratory a still whichutilizes a mercury vapor heating jacket.

An improved laboratory scale equilibrium flash distillation still hasnow been developed which has eliminated the operability problems andthose associated with the use of a mercury vapor heating means. Thus,the improved flash distillation still of the present invention can beused to process various crude hydrocarbons in producing petroleumasphalts and corresponding vacuum gas oils of the quality normallyexpected from only commercial operations. Further, by substituting amolten salt bath for the more hazardous mercury vapor heating means usedby existing laboratory stills, the flash still of the present inventioncan be operated in distillation laboratories without the problems anddangers associated with mercury vapor heating.

The equilibrium flash still of the present invention broadly comprises aflash zone, a preheating zone and a heating zone, with the preheatingzone surrounding the flash zone and the preheating zone and flash zonebeing disposed within the heating zone; means for introducing a heattransfer medium into the heating zone, means for removing the heattransfer medium from the heating zone, means for heating the heattransfer medium in the heating zone, means for introducing feedsequentially into the preheating zone and then into the flash zone, afirst removing means for recovering the light end product from the flashzone, a second removing means for recovering the heavy end product fromthe flash zone and means for maintaining the first and second removingmeans at an equalized su'batrnospheric pressure.

The present invention will be more fully understood from the detaileddescription hereinbelow and the accompanying drawings wherein FIGURE 1shows a distillation apparatus incorporating the still of thisinvention;

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FIGURE 2 is a sectional elevational view of the still;

FIGURE 3 illustrates details of the bottoms adapter for the distillationapparatus; and

FIGURE 4 illustrates details of the overhead adapters.

More specifically, the equilibrium flash still of the present inventioncomprises a flash chamber 10, a preheating coil 12, and a heating vessel14 with flash chamber 10 and preheating coil 12 being arranged withinthe heating vessel. Preheating coil 12 consists of tubing which is woundaround, and in contact with, flash chamber 10 from the upper to thelower portion thereof. Feed material passes from the outside connection16 of coil 12 through the coil 12 which serves to preheat the feed. Thepreheated feed is then introduced into the flash chamber 10 tangentiallyat a point slightly above the bottom portion thereof through opening 18(see FIGURE 2). Heating vessel 14 surrounds flash chamber 10 forsubstantially its entire length and is provided with closures at itsbottom and its top. The closure at the bottom includes a packed glandexit opening 20 which has a bottoms recovery line 22 extendingtherethrough. The closure at the top is removable and includes a fillport 24 through which the heat transfer medium 32 can be introduced intothe heating vessel 14, a stirrer port 26 and a thermowell 28. Stirrerport 26 is provided so that the heat transfer medium 32 can be gentlyagitated by a stirrer (not shown) to maintain uniform temperaturesthrough the entire bath. Therm-owell 28 is provided to permitmeasurement of the temperature gradient in flash chamber 10. Electricimmersion heaters 30 are arranged in vessel 14 to supply the heat tomaintain the heat transfer medium in a molten state. Heaters 30 arepowered by an electric source which can supply suflicient electric powerto heat the heat transfer medium, e.g., up to about 400 watts perheater, which source is not shown. The heat transfer medium 32 used inthe present invention is, for example, a molten salt bath, such assodium or potassium salts. Skin thermocouples 34 are spaced on theoutside surface and along the entire length of the heating vessel 14 tofurnish temperature data 'for temperature control. Several inches ofinsulation 36 on vessel 14 serve to limit heat loss from the vessel. Adrain 38 is provided in vessel 14 for drawing oil the heat transfermedium when desired, such as when the apparatus is not being used.

Flash chamber 10 has in addition to a bottoms recovery line 22, anoverhead vapor line 40. A shut-off valve 42 is located in the bottomsrecovery line 22 which line then enters a liquid seal device 50 withinbottoms adapter, generally designated by numeral 44, which is providedwith a. plugged access port 46 and drip rod 48. The bottoms pass throughline 22 into the seal device 50, i.e., an overflow cup, and then toreceiver assembly 52. The bottoms line 22 and shut-off valve 42 areenclosed by an electric heater 54 which insures optimum heat control andsample protection.

Overhead vapor from flash chamber 10 passes through vapor line 40,condenser 56, e.g., air or water cooled, and a quick-opening diaphragmvalve 58 into an overhead receiver assembly, i.e., overhead adapter 60.Overhead adapter 60 is attached to overhead receiver 62 and includes adrip rod 64 which extends into the overhead receiver. The overheadproduct passes from overhead adapter 60 to the overhead product receiverassembly 62 which is identical with the bottoms product receiverassembly 52. A vacuum controller 66 maintains the overhead vapor line 40and bottoms recovery line 22 at equal ized subatmospheric pressures andprovides satisfactory pressure stability down to about 1 mm. Hg. Stillpressure is measured through a tap '68 in the overhead line 40 below thecondenser 56 by a pressure measuring device (not shown) such as aDubrovin gauge a closed end mercury manometer or, at higher pressures,by an open end mercury manometer. Suitable manometers indicate thepressure at each receiver for control of pump-out pressures ordifferential settings. An adjustable liquid level bubbler may be used toprovide a pressure differential between the overhead and bottomsreceivers, thus providing control on the liquid level within the flashchamber. Howunder vacuum, taking cuts to a 650 F. atmospheric boilingpoint. The vacuum bottoms (35.6 volume percent on crude) are nextflashed in the flash still of the present invention at 680 F. Severalruns are made at various pressures. The flash chamber conditions, alongwith the feed, gas oil and bottoms yield and quality measurements arelisted in Table I.

TABLE I.-MIDGET STILL VACUUM FLASH DIS'IILLATION OF 35.6 VOL. PERCENTMID- CONTINENT REDUCED CRUDE Pressure, mm. Hg

Temperature, F Liquid, pereelni; on crude.

Pour, E Flash, COC. Aniline Point,

Reduced Gas Oil Overhead Crude ever, this unit can be operated withoutthis device, and although the liquid level may be below the heatingvessel, there is no evidence of deterioration in product quality.Operation of the equilibrium flash still is as follows: Heat transfermedium, e.g., salt, is introduced through fill port 24 until flashchamber 10 is substantially surrounded. Electric immersion heaters arethen turned on and the medium heated to the desired operatingtemperature. Flash chamber 10 is then evacuated to the desired operatingpressure and the feed, which is measured by scale 70, is pumped 72 fromtank 74 through line 16 into preheat coil 12 to be introduced into thelower portion of the flash chamber at inlet 18. The feed is cracked intothe resulting products in chamber 10.

Feed rates of about 50 to 200 grams per hour are generally used in theflash still and upon introduction of the feed into the bottom of theflash chamber 10, the vapor liquid equilibrium is essentially complete.The flash still is generally run at a temperature of about 680 F. to 740F. Temperature control is not a problem in the distillation apparatus ofthe present invention and thus when using the heat transfer medium,e.g., molten salt bath, temperatures of up to 800 F. and even higher arenot considered excessive in this type of unit.

The flash still has proved to be very valuable in that it can be usedfor a variety of feedstocks such as reduced crudes, heavy residues,penetration asphalt, and even feedstocks yielding zero penetrationbottoms, which can be handled by the use of auxiliary heat sources suchas infrared lamps. These lamps can be assembled promptly when needed andremoved when the condition Warrants. The still has also proven to bevery useful in crude assay work, producing petroleum asphalt andcorresponding vacuum gas oils of the qualities to be expected fromcommercial operations. Example I demonstrates such use.

EXAMPLE I A mid-continent crude is fractionated on a glasstrueboiling-point still yielding cuts to a nominal 400 F. end point. Thecrude is further reduced on the same still EXAMPLE II To furtherillustrate the versatility of the still, a severely cracked residual isflash distilled at two different sets of conditions. Yields and productquality measures on the gas oils and asphalt bottoms are listed in TableII. The high viscosity and low penetration of bottoms produced are ofparticular interest from the standpoint of the operability of the still.

TABLE II.MID GET STILL VACUUM FLASH DISTILLATION OF A SEVERELY CRACKEDRESIDUAL OIL Flash temperature, F 740 678 Flash pressure, mm. Hg 30 10Gas oil overhead:

Yield, Wt. percent of feed 47. 0 40. 0 Gravity, API 19. 6 19. 6 Carbonres., rams 1. 248 0. 951 Wt. percent:

Carbon 86. 83 86. 59 11.71 11. 72 0.771 0.727 0. 34 0.35 399 392 s:Yield, wt. percent of feed 53. 0 60.0 Gravity, .API 1. 0 2.8 Carbonres., con 35. 74 32.14 N05 insolubles, Wt percent 28. 66 22. 54 Furolvis. at 27 213.0 Penetration, 77 F 5 12 It 1s claimed:

1. A laboratory scale flash still for separation of a petroleum fractionwhich comprises a preheating coil and a vertically disposed flashchamber, said preheating coil being wound externally about said chamberfrom the upper to the lower end thereof and interconnecting at its lowerend with the interior lower section of said flash chamber for deliveringthe preheated petroleum fraction thereto for flash distillationseparation of said fraction, an enclosed heating vessel substantiallysurrounding said preheating coil and flash chamber, said heating vesselcontaining a molten salt heat transfer medium and a heating means insaid heat transfer medium for maintaining said medium at a predeterminedtemperature, a charge pipe for introducing the petroleum fraction feedinto said preheating coil at its upper end an overhead recovery meansnear the top of said flash chamber for removing the light end productfrom said flash chamber, a bottoms recovery means near the bottom ofsaid flash chamber for removing the heavy end product from said flashchamber, and a vacuum controller means for maintaining both of saidrecovery means at equalized subatmospheric pressures.

2. The still of claim 1 wherein said flash chamber comprises anelongated flash chamber.

3. The still of claim 1 including insulating means surrounding saidheating vessel.

4. The still of claim 3 wherein said bottoms recovery means includes aseal means comprising an overflow cup, and a bottoms recovery lineinterconnecting the bottom of said flash chamber and the interior ofsaid overflow cup.

5. The still of claim 4 wherein said bottoms recovery means includes areceiver and said overflow cup has a drip rod thereon adapted to passliquid from said cup to said receiver.

References Cited UNITED STATES PATENTS 754,687 3/1904 ONeall 196-981,266,281 5/1918 Lapp 1961 14 1,990,831 2/1935 Lea 202-177 2,224,01412/1940 Dunham et al 23288.4 2,226,828 12/1940 Moran 202-177 2,310,3992/1943 Cox et al. 202-205 2,642,386 6/1953 Piros 202177 2,702,268 2/1955Egger et al. 203-100 2,751,281 6/1956 Cohn 23255 NORMAN YUDKOFF, PrimaryExaminer. F. E. DRUMMOND, Assistant Examiner.

